Recently the UK Disability Discrimination Commission evaluated the
accessibility of 1000 UK websites.
http://www.drc-gb.org/publicationsandreports/report.asp
They used a number of methods including bobby checks, expert reviews
and real user tests. Interestingly they state that.
"As many as 45% of the problems experienced by the user group were not
a violation of any Checkpoint, and would not have been detected without
user testing."
and concluded that
"It is clear that compliance with the technical guidelines and the use
of automated tests are only the first steps towards accessibility:
there can be no substitute for involving disabled people themselves in
design and testing, and for ensuring that disabled users have the best
advice and information available about how to use assistive technology,
as well as the access features provided by Web browsers and computer
operating systems."
I'm personally interested in how the WAI guidelines were derived. Are
they a result of comprehensive user testing, or simply recommendations
from accessibility experts?